VFX 728  /  Spring 2026  /  Fowler

Exercise 1 – Procedural Seashells: VEX/VOP Seashell Generator

Date Assigned:	Class 1
Date Due:	Class 4

Checklist

Goals

Your goal is to create a seashell generator using VEX (snippets) and VOP. The basic formulas will be discussed in class. The goal is to learn VOP SOPs as well as VEX code as given, in order to achieve this task and produce a sophisticated modeling tool.

VEX/VOP can play a large role in procedural effects and it is important to be familiar with both. This exercise will allow you to practice the syntax of both VEX and VOP.

Requirements

The following are the minimum requirements for this exercise:

Create a seashell generator using VEX and VOPs as outlined in class.

• The design of the seashell should be changeable through parameters.
• Parameter names should make sense to someone who has never seen the formula for seashells but just wants to use the program.
• Your VOP network should be neatly organized.
• Make it easy to see that both VEX and VOP are capable of producing the same shell — for example, a switch node with the same parameters for one shell should be included.
• Show that the generator can produce more than one type of seashell (five types expected). This should be evident in your hip file and/or visual.
• Your VEX code must be commented to show understanding.
• [optional] A render or animation demonstrating results from your seashell tool.

Sensible parameter names should be used. There are various ways the general method shown in class could be extended, such as adding the ability to have user-defined curves. Your program should have the ability to create several types of shells. Enhancements to the general modeling tool need not be in VEX — you are allowed to use whatever node network you choose.

Considerations

You will create a procedural system for generating seashells. Building seashells using VEX was demonstrated in class. The shape of seashells and their generation is described in:

• Modeling Seashells — Siggraph 92: algorithmicbotany.org/papers/shells.sig92.pdf
• The Algorithmic Beauty of Sea Shells — amazon.com

There has long been a fascination with spiral patterns in nature, and in particular seashells. They are the subject of various photographic studies — one personal favorite is Andreas Feininger, a famous photographer whose compositions of seashells stem from his fascination with their structure. There is a BBC interview with him from 1983 on YouTube:

youtube.com/watch?v=LXGua_YjiUg

Spiral patterns seen in nature are also imitated in architecture. For those who did the spiral staircase exercise in VSFX 350, here's an extra challenge — a spiral escalator by Ken Perlin:

mrl.nyu.edu/~perlin/escalator

There is also an interesting demonstration by Stephen Wolfram of the basic concept:

youtube.com/watch?v=yqWN_nrQ-B0

What is expected in this class is a more complete demonstration of your generator. Examples of how these shells have been used in images and animations are available on the student examples page in the quarterly reels.

Submission Guidelines

Submit a directory named:

S26_V728_E1_LastnameFirstname_Shells/

S26_V728_E1_LastnameFirstname_Shells/
├── S26_V728_E1_LastnameFirstname_Shells.hipnc
├── S26_V728_E1_LastnameFirstname_Shells.jpg     (optional but strongly encouraged)
├── S26_V728_E1_LastnameFirstname_Shells.mp4     (optional but strongly encouraged)
└── tex/                                          (if textures used)
    └── filenameOfImage

This directory must contain:

• S26_V728_E1_LastnameFirstname_Shells.hipnc — this should include a VEX SOP and a VOP SOP version. The VEX code must be commented. Make it clear that you have created working versions of both — an example using the same parameters with each method and a switch node to show the same result is required.
• S26_V728_E1_LastnameFirstname_Shells.jpg and .mp4 [optional but strongly encouraged] — should demonstrate the range of seashells your tool can produce.
  Note: always render to EXR; convert to JPG/PNG using mplay, Photoshop, or IrfanView. Any file > 1 GB will not be accepted. Use Handbrake (free, Windows) with H264x codec.
• If textures are used, include a tex/ directory. Be sure that paths are relative in your shaders using the $HIP global variable (e.g., $HIP/textures/filenameOfImage) — not absolute paths.

Grading (out of 10)

This is a warm-up exercise. Satisfying the minimum requirements earns an 80%. Doing less will result in a lower grade; going further will result in a higher grade. See rubric.

What Professor Fowler is looking for:

• Have you created a working VEX version and a VOP version?
• Is a switch node included showing both produce the same result?
• Is your VEX code commented to demonstrate understanding?
• Are your parameter names sensible to a user unfamiliar with the formulas?
• Can your tool produce at least five distinct shell types?
• Is your VOP network neatly organized?

Pushing further:

• Demonstrate exploration beyond the specifications.
• Produce a high-quality visual or animation showing the range of your generator.
• Creativity and aesthetics count toward moving your grade above 80%.

Minimum requirements met:	8 / 10
+ Properly submitted:	8.5 / 10
+ Exploration, understanding, high-quality visual:	9–10 / 10